fix test

Author: misos1

packages/camera/camera_avfoundation/example/ios/RunnerTests/FLTCamSampleBufferTests.m

@@ -313,6 +313,11 @@ - (void)testStartWritingShouldNotBeCalledBetweenSampleCreationAndAppending {
         videoAppended = YES;
       });
 
+  id inputMock = OCMClassMock([AVAssetWriterInput class]);
+  OCMStub([inputMock assetWriterInputWithMediaType:OCMOCK_ANY outputSettings:OCMOCK_ANY])
+      .andReturn(inputMock);
+  OCMStub([inputMock isReadyForMoreMediaData]).andReturn(YES);
+
   [cam
       startVideoRecordingWithCompletion:^(FlutterError *_Nullable error) {
       }